In semiconductor technologies, critical-dimension (CD) variations can be induced by certain “effects” that occur during an etching process. Examples of such effects include the “sandwich effect,” which is caused by the nearest spacing around the main pattern, and the “loading effect,” which is related to the ratio of open areas and non-open areas. The effects tend to differently alter isolated patterns and dense patterns. The resulting variation in CD can be as high as 20 nanometers in one example.